A biomechanical model for measurement of lower extremity kinematics with integrated multisegmental foot motion

Three-dimensional gait analysis is a frequently employed tool for surgical planning, motion characterization, and outcomes analysis in a variety of clinical and research settings. Patients with a variety of diagnoses (e.g. cerebral palsy, myelomeningocele, posterior tibial tendon dysfunction) can benefit from the information provided by such an analysis. Current models for assessing lower extremity motion during gait benefit from ease of clinical implementation, but underlying assumptions regarding joint location and distal segment motion limit their effectiveness and accuracy. The currently employed anatomic model is specifically limited in its estimation of hip joint center location and its representation of the foot as a single segment. The intent of this study was to integrate measurements of multisegmental foot kinematics into a standardized lower extremity model, using radiographic referencing methods to calculate orientations of bony axes based on surface marker orientations. Improved methods of estimating hip joint center location were also incorporated into the new model using functional methods. This results in a kinematic model that can report segmental kinematics from toe to pelvis, with a multisegmental perspective on foot motion. The new model was applied to a population of ten healthy young adults instrumented for gait analysis. Gait kinematics reported by the new model were compared to output from standardized models applied to the same data trials. Results demonstrated high correlation between models, with intra- and inter-session repeatability measures comparable to the established clinical standard. Secondary analysis of kinematic output showed sensitivity to radiographic parameters in a number of measures. Overall results suggest that this model is appropriate for use in both clinical and research settings, although some modification for clinical convention may be necessary for optimal use in treatment planning